Implantable medical devices (IMDs) often rely on sensors to detect physiological signals for monitoring a patient condition and/or determining a need for delivering a therapy. Acoustic sensors are one type of sensor that may be used to detect physiological signals within the body. For example, heart sounds detected by acoustic sensors are useful in detecting abnormal heart function. Other physiological signals that may be sensed using acoustic sensors include intestinal sounds and lung sounds.
Some IMDs are capable of generating a patient alert signal to notify the patient of a condition requiring medical attention or a response by the patient. A patient alert condition may be related to the function or status of the IMD itself or a physiological condition detected by the IMD. A patient alert signal may be an audible signal emitted by an acoustic element.
An acoustic element, such as a piezoelectric transducer, used for emitting a patient alert signal is typically activated using a high frequency signal, for example on the order of 800 to 1,200 Hz. Acoustic signals sensed for detecting heart sounds may have a frequency of about 15 Hz to 400 Hz. For at least this reason, a circuit for generating an acoustical patient alert and a circuit for sensing acoustic signals each have different operational requirements. As such, such acoustical patient alert and acoustical sensing circuits have been implemented separately using separate acoustic elements.